A Senate panel has released documents on a June 2016 meeting between top Trump campaign aides and a Russian delegation promising political "dirt".
The 2,500 pages of transcripts include interviews with Donald Trump's eldest son, Donald Trump Jr, who met a Russian lawyer ahead of the 2016 election.
The lawyer, Natalia Veselnitskaya, denies working on behalf of Moscow.
The meeting is a part of an ongoing probe by the US Department of Justice into alleged Russia meddling in 2016.
What are the key things the documents tell us?
Donald Trump Jr confirmed he said 'I love it'
After the British music publicist who arranged the meeting, Rob Goldstone, suggested he had access to "official documents and information that would incriminate" Democrat Hillary Clinton, Trump Jr replied in an email saying "if it's what you say, I love it, especially later in the summer".
In his Senate interview, Trump Jr called his use of the phrase a "colloquial term" to say "great, thank you" for "potential information about an opponent" - namely, Hillary Clinton.
The BBC's Anthony Zurcher: Trump Jr's "If it's what you say, I love it" email was one of the most explosive revelations when news of the June 2016 Trump Tower meeting was first made public.
He says he doesn't recall how he felt about being told that Russia and its government wanted to support his father's campaign. He also doesn't go into detail about why he would love it "especially later in the summer".
Details of the emails and documents hacked from the Democratic National Committee server would first start becoming public, through Wikileaks and similar channels, later in the summer.
The blocked number question
Donald Trump Jr received a call from a blocked number on 6 June, three days before the meeting.
It lasted four minutes and came sandwiched between two phone calls Trump Jr had with Emin Agalarov, an Azerbaijani-Russian businessman and music star who was pushing for the Trump Tower meeting.
When asked whether the call might have been the president, who is known to use a blocked number, Trump Jr replied: "I don't know."
AZ analysis: Trump Jr denies any communications with his father about the meeting before or after it took place.
But the day after the blocked call - and two days before the Trump Tower meeting - the elder Trump announces that he would be making a "major speech" the following week "discussing all of the things that have taken place with the Clintons".
That speech never happened.
Trump Jr said his father may have influenced misleading statement
Trump Jr has repeatedly said he did not know of any direct involvement by his father in drafting an explanation for the meeting that subsequently turned out to be untrue.
But he did say "he may have commented through Hope Hicks", his former spokeswoman.
AZ analysis: Trump Jr's memory once again fails him, this time when it comes to exactly how involved his father was in helping craft the original - misleading - explanation that the June 2016 Trump Tower meeting was to discuss adoption policy.
That, certainly, was one of the topics - but as Trump Jr's email chain revealed, the presidential son was initially more interested in learning what dirt the Russians might have on Mrs Clinton.
Trump Jr doesn't completely close the door on Trump's involvement in the White House damage control operation, however, suggesting that he may have offered edits on the original statement through his long-time communications aide, Hope Hicks.
The reason this is relevant is that it could be evidence that the president was engaging in a cover-up to hide the nature of the Trump Tower meeting.
Mueller is reportedly reviewing the actions taken as part of his investigation into whether anyone in the White House - including the president himself - took actions that could constitute obstruction of justice.
Misleading the public or the media itself is not illegal, but attempts at deception could be evidence of a larger effort to conceal potentially incriminating actions.
Paul Manafort's notes are now available
Manafort, who was the campaign manager at the time of the meeting, took brief notes during the meeting, which included words like "Offshore - Cyprus", "133m shares" and "Illici".
AZ analysis: What is "Illici"? Is it a typo? A super-secret society? Who or what are the "active sponsors of RNC" - and does RNC stand for the Republican National Committee?
The island nation of Cyprus pops up twice in the list, which is where American-born financier Bill Browder - also named on the list - conducted much of his Russia-related business. Browder, who renounced his US citizenship and currently lives in the UK, was a leading advocate for the Magnitsky Act through which the US Congress imposed sanctions on Russia for human rights violations.
Sergie Magnitsky was a Browder accountant who died in a Russian prison under questionable circumstances.
Manafort's list is cryptic, and he declined an opportunity to speak to Senate investigators. The former Trump campaign chair is currently under indictment by Robert Mueller on charges of money laundering and unregistered foreign lobbying conducted before he joined the Trump team.
Goldstone was pressured to set up the meeting
Goldstone said his client Emin Agalarov, Azerbaijan's biggest pop star and son of Russian billionaire Aras Agalarov, pressured him into setting up the meeting with Trump Jr - even after Goldstone said it was "a really bad idea".
"He said, 'it doesn't matter. You just need to get the meeting.'"
AZ analysis: One of the things that comes through in the committee documents is exactly how eager the Agalarovs were to set up this meeting with the Trump campaign's senior staff.
Emin Agalarov exchanged voicemails with Trump Jr. They may have actually spoken (Trump Jr says his memory is fuzzy.) The Agalarovs also pushed Goldstone to make the meeting happen.
Did that cause Goldstone to exaggerate what the Russians had to offer Trump Jr as far as information on Hillary Clinton went? Perhaps.
On the other hand, it seems like the Agalarovs - and Goldstone - went through an awful lot of work to set up a meeting where Natalya Veslinstkaya and her associates only wanted to talk about adoption policy and sanctions imposed by the Magnitsky Act.